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The Buzz on RoomAir Cleaners

By Gregory Alford

Asthma can be triggered by both indoor and outdoor airpollution. There isn’t much we can do to avoid the out-side air pollution, but what about improving the qualityof the air inside our homes? It makes sense that if wecould clean the allergens and irritants from the air webreathe indoors, our asthma would be better man-

aged—especially given that Americans spend 90% oftheir time indoors. The problem is that the medical studiesjust don’t back this up. Indoor air filters alone do notseem to have much of an impact on improving asthmacontrol. But air filtration systems are often recommendedas part of an overall strategy of environmental controls.

How Effective are They for Management of Allergies and Asthma?

The Value of Air Filtration

The Lung Association and the EnvironmentalProtection Agency (EPA) both support the use of air fil-tration devices; however, both state they should not bethe primary method used to reduce indoor allergens.Wellington S. Tichenor, MD, an allergist in New YorkCity, agrees.

According to Dr. Tichenor, basic environmental con-trol methods are the most effective way to reduce com-mon allergens such as dust mites, pollens, and animaldander in indoor air. Purchasing furniture that does notcollect dust, keeping the humidity level below 50%,using effective cleaning methods, keeping animals out-side, and not letting anyone smoke inside are essentialfor controlling allergies and asthma.

Bedrooms are usually an excellent place to employstrategies proven to reduce allergens because it is wherepeople spend the most of their time. “The ideal bed-room consists of a wooden or steel bed with a mattressand pillow (made of a nonallergenic material) coveredwith an allergy-proof mattress and pillow cover, cottonsheets, a blanket that is washed weekly in hot water,wooden or tile floors, and shades on the windows,” saysDr. Tichenor, adding that no other furniture should bein the room. “I’ll tell you that almost nobody goes thatfar, but it’s important to understand the maximum thatcan be done.” Air filters can be helpful when used inconjunction with the environmental control methodsjust listed, but they should not replace these measuresthat have a long track record of effectiveness.

“If you are thinking, ‘I’ll skip all of the above (envi-ronmental control measures) and buy the expensiveroom air cleaner I saw on TV—that will solve all of myallergy problems!’ you may have even more trouble,”says Mark Corbett, MD, an allergist in Louisville, Ky.“You may no longer have money left for your medica-tion and you’ll still be miserable. [Air filters] can behelpful, but only when used with other environmentalcontrol measures.”

To complicate matters further, air filtration systemsare only able to rid the air of certain types of harmfulparticles. If an allergen or irritant particle is heavy, theparticles released in the air do not stay airborne for long,therefore, the filter cannot trap it or remove it from theroom. Air filtration units can be effective in trappinganimal dander, tobacco smoke, and certain pollen parti-cles. These substances are light and can remain airbornefor long periods. It is therefore important to knowwhich indoor substances trigger your allergies and asth-ma to determine whether a filtration device would beuseful for you.

Robert A. Wood, MD, associate professor ofimmunology and allergy at Johns Hopkins Children’sCenter in Baltimore, Maryland, explains this further.

“HEPA [high efficiency particulate air] or electrostaticair filtration devices can be very effective in reducing air-borne levels of animal allergens, especially when carpet-ing is removed or cleaned thoroughly and frequently. Incontrast, any air filtration device has much less effectreducing airborne levels of dust mite or cockroach aller-gens. These allergens are carried on larger particles thatdo not remain airborne for any length of time and aretherefore less likely to be trapped.”

What Type of Air Filters Are MostEffective?

Wood recommends single-room air filtration units, asthey tend to be more effective than filters placed in aforced air heating or cooling system. However, whenpurchasing a unit for a room, make sure it is capable offiltering enough air for the square footage of the room.A rule of thumb is that a unit should be capable ofcleaning the air in a room every 4 to 6 minutes.

If you plan to purchase a room air filtration unit, itwill take some time and effort to sort through the differ-ent products available. Most units cost under $300,weigh between 10 and 20 pounds, and can be placed onthe floor or on a table. There are five basic types ofunits.

• Mechanical filter units force air through a specialmesh that traps tiny particles. The best of theseunits use HEPA filters. HEPA filters remove at least99.97% of particles at least 0.3 microns in size.

• Electrostatic filter units create a static charge on thefilter to allow airborne particles to stick to the filter.

• Electrostatic precipitator units create oppositecharges on metal plates or wires in a filter assembly.Pollen, smoke, and other particles stick to the col-lecting plate that contains an opposite charge.

• Ionization units emit a small charge to the air,which creates a magnetic-like attraction that causesparticles to stick to the filter or other surfaces.However, some of these units create harmful ozone.

• New entries into the market include units that heatthe air to sterilize it.

At this time, there is no single way to judge the per-formance of competing units. Although the Associationof Home Appliance Manufacturers (AHAM) tests andrates room air cleaners, not every manufacturer partici-pates. Consumer Reports finds AHAM’s clean-air deliveryrate (CADR) measurement is a reliable indication ofhow well particular filters trap tiny particles, as well asand how much air the unit moves.

AHAM recommends purchasing a unit with a CADRthat is two thirds the square-foot measurement of theroom the air filter will be used in. In addition, check thelabel or box for a measurement of airflow measured incubic feet per minute. The faster the flow, the quicker

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the room air is cleaned. In addition, look for informa-tion from the American Society of Heating,Refrigeration, and Air-Conditioning Engineers(ASHRAE). ASHRAE certification offers an informa-tive measure of cleaning based on the percentage of aircontaminants effectively filtered by the unit.

The October 2003 edition of Consumer Reportskicked up more than a little dust when its test resultsfound that many of the most popular and heavily adver-tised electrostatic and ionizing units were among theleast effective. A subsequent retest conducted by themagazine at the request of several manufacturers con-firmed its earlier findings. Several manufacturers havecriticized the report, saying that the testing methods didnot conform to real-world conditions.

The EPA estimates that there are 15 million room aircleaners currently in service. However, it is importantfor people to realize that purchasing a room air filtra-tion unit is not a shortcut to better asthma control. Itcan, however, be an important part of an overall pro-gram of environmental controls. Discuss with yourhealth care provider whether a room air filter might be ahelpful addition to your asthma management plan,given the specific indoor substances that trigger yourallergies and asthma.

Gregory Alford is a freelance writer from Rockford, Ill.

Reprint orders:Elevier, Inc., 11830 Westline Industrial Dr., St. Louis,MO 63146-3318; phone (314) 453-4350.doi: 10.1016/j.asthmamag.2004.

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■ The Association of Home Appliance Manufacturers: www.cadr.org

■ American Lung Association: www.lungusa.org

■ American Academy of Allergy Asthma and Immunology: www.aaaai.org

■ Consumer Reports (subscription site): www.consumerreports.org

Contacts for More Information About Air Filters

■ What substances will the cleaner remove from the air in my home? What substances will it not remove?

■ What is the efficiency rating of the cleaner in relation to the “true HEPA” standard?

■ What is the device’s CADR?

■ How difficult is it to change the filter? How often does it have to be changed? How much do filters cost? Arethey readily available throughout the year?

■ How much noise does the unit make? Is it quiet enough to run while I sleep?

The Asthma and Allergy Foundation of America created a list of questions for people to ask when shoppingfor room air filtration units. The questions include the following: